蒙脱石-复合氧化物界面核素竞争络合机制研究

Montmorillonite is an eological mineral candidate for stably buffering nuclear waste. It is also an environment friendly material for causing nuclide to be back stability to nature. Nowadays, a disposal technique for strengthening the buffer layer is to add primary composite oxide minerals. Here, the nuclides and positive (negative) ions at the calcium-based montmorillonite-complex oxides interface are chose as a research system. Monte carlo, molecular dynamics, density functional theory and two-dimensional correlation analysis methods are used to quantitatively calculate the accumulatived change of complex interfaces, such as charge compensation mechanism, defects and electron transfer processes, etc, by effective of weak thermo-hydro-pH-chemical (THPC) coupling-type class geological disposal conditions. The mechanism of "electron-valence-atom-bond-interface" multi-scale atom diffusion and electronic transition is comprehensively analyzed in the process of dynamic adsorption/desorption. Finally, the theoretical and experimental evaluation methods about microscopic oxidation-reduction processes in the montmorillonite-complex oxide interfaces will be bulit under THPC coupling condition. Such a system could provide a theoretical basis for the selective retardation of actinide nuclides wastes and the evaluation of damage accumulation.

蒙脱石被认为是一种稳定阻滞核废物的地质矿物候选物，并使核素稳定回归自然的环境友好化材料。目前，强化缓冲层的热点处置手段是添加原生复合氧化物矿物。本项目以钙基蒙脱石-复合氧化物界面核素和阳（阴）离子为研究对象，拟采用蒙特卡罗、分子动力学、密度泛函理论和二维相关数据分析技术相结合的方法定量地计算复合界面受模拟地质处置环境（微量“热-水-pH-化学”（THPC）耦合）引起的缺陷、电荷补偿、电子转移等积累性转变规律。综合分析动态吸附/解吸附过程中“电子-价态-原子-结合键-界面”多尺度原子迁移和电子转移机制。最终，建立THPC耦合蒙脱石-复合氧化物界面缓冲核素络合物的微观氧化还原过程的理论与实验评价方法。该项目的研究成果将为选择性阻滞锕系核素废料和缓冲层积累性损伤评价研究提供理论依据。

蒙脱石被认为是一种稳定阻滞核废物的地质矿物候选物，并使核素稳定回归自然的环境友好化材料。目前，强化缓冲层的热点处置手段是添加原生复合氧化物矿物。本项目以钙基蒙脱石-复合氧化物界面核素和阳（阴）离子为研究对象，采用定量计算和实验法讨论了复合界面受模拟地质处置环境（微量“热-水-pH-化学”（THPC）耦合）引起的缺陷、电荷补偿、电子转移等积累性转变规律。研究发现，铀酰可选择性截断蒙脱石-复合氧化物四-八面体界面间电子气，形成蒙脱石-复合氧化物-铀酰间U-O-Fe长程氢键，且腐殖酸介导体增强了长程键轨道强度。进而，根据此特性设计了系列蒙脱石-复合氧化物选择性去除共存铀酰-金属离子实验，验证了模拟的可靠性。其中，在腐殖酸介导下蒙脱石-改性磁铁矿-闪锌矿的界面和孔道间赋存铀酰量高达462.96 mg·g-1和696.58 mg·g-1，可媲美现有有机去除剂。此外，综合评价了有机酸活性基团对蒙皂石族黏土的损伤作用，发现“夹角”构型增加了层间负电层附着位点，其是阴离子（活性基团）诱导增强铀酰-重金属离子发生络合反应的根本方式。本项目的研究成果将为膨润土选择性阻滞锕系核素废料和缓冲层积累性损伤评价研究提供理论依据。